Final answer:
During normal operation, the calculated FMS position is based on inputs from GPS, IRS, and various other navigational systems, which the FMS integrates to maintain accurate positioning.
Step-by-step explanation:
The calculated Flight Management System (FMS) position during normal operation is typically based on a combination of various navigational inputs. These inputs include: data from Global Positioning System (GPS), Inertial Reference Systems (IRS), DME/DME (Distance Measuring Equipment) updating, VOR/DME (Very High Frequency Omnidirectional Range/Distance Measuring Equipment), and sometimes inputs from other navigational aids like ADF (Automatic Direction Finder) or ILS (Instrument Landing System) when appropriate. The FMS integrates data from these systems to generate a synthesized aircraft position which is then used for enroute navigation, approach, and departure procedures ensuring accuracy even when one or more systems might be degraded or unavailable.